1. Field of the Invention
The present invention relates to an acetic acid assimilating gene of Escherichia coli, the polypeptide encoded by this gene, recombinant plasmids containing this gene, bacteria which have been transformed with such plasmids, and a method of producing a product by culturing such bacteria.
2. Discussion of the Background
When glucose is added to the medium for liquid culture of E. coli, acetic acid is released from the cells which assimilate (metabolize) the glucose, so that the pH value of the medium is lowered with the passage of the culture time and the growth of the cells, which is well known. Lowering of the pH value of the medium inhibits growth of the cells, which, therefore, is a serious problem in the production of products such as amino acids by fermentation.
Some attempts to overcome the problem by improvement of the cells to be cultured have heretofore been made by some groups. For instance, Bauer et al. utilized a strain having a deletion in the route by which acetic acid is produced in the production of IL-2 by fermentation, by employing a mutant having a defective phosphotransacetylase. When culturing this strain, acetic acid was not accumulated in the medium, and the growth of the cells was not inhibited (Keith A. B. et al., Appl. Environ. Microbiol., 56:1296, 1990). Matsuyama et al. succeeded in isolating a gene encoding an acetate kinase (ackA) which participates in the route of producing acetic acid by E. coli (Asahi M. et al., J. Bacteriol., 171:577, 1989) .
However, there remains a need for alternative methods for improving the culture of E. coli when using glucose as a nutrient.